Ronald S Jones

Reversal of profound rocuronium block monitored in three muscle groups with sugammadex in ponies

BACKGROUND This clinical study evaluated the speed of reversal of profound rocuronium block in ponies using sugammadex and investigated the differences in onset and recovery from block in three different muscle groups. METHODS Anaesthesia was induced and maintained with isoflurane in oxygen 100% in eight ponies. Neuromuscular monitoring was performed at each site using acceleromyography: in the extensor muscles of the pelvic limb (peroneal nerve) and thoracic limb (radial nerve), and in the orbicularis oris muscle (OOM; facial nerve). Rocuronium 0.6 mg kg(-1) i.v. was administered, followed 5 min later by sugammadex 4 mg kg(-1) i.v. Onset time (onsetROC), maximum block, and time to recovery of the train-of-four ratio to 0.9 (TOFR=0.9) were recorded. The differences between monitored sites were compared using one-way anova followed by a post hoc Dunns test. RESULTS Onset of ROC was significantly delayed in OOM compared with both limbs [pelvic limb, thoracic limb, and OOM: 43.1 (sd 16.9), 50.6 (15.9), and 204.4 (35.8) s, respectively; P<0.001]. Complete block was achieved in the pelvic and thoracic limbs, but in none of the eight ponies in the OOM [mean T1=15.3 (9.4)%; range: 7-36%]. No differences were observed between muscle sites in recovery to TOFR=0.9 [pelvic limb, thoracic limb, and OOM: 2.3 (0.9), 3.4 (1.7), and 2.8 (2.1) min, respectively]. No adverse effects of sugammadex were detected throughout the study period. CONCLUSIONS Sugammadex can be used to reverse profound rocuronium-induced block in ponies during isoflurane anaesthesia. Thoracic limb muscles represent a suitable alternative for monitoring neuromuscular block compared with pelvic limb muscles.

Isoflurane to prolong medetomidine/ketamine anaesthesia in six adult female chimpanzees (Pan troglodytes)

Six adult female chimpanzees (Pan troglodytes) were anaesthetised for the placement of intrauterine contraceptive devices, microchips for identification, routine blood sampling, and physical measurements. Anaesthesia was induced with medetomidine in combination with ketamine administered by intramuscular injection with a projectile syringe. Induction was smooth and rapid, but five of the animals were insufficiently relaxed for orotracheal intubation. The plane of anaesthesia was deepened by administering isoflurane delivered in oxygen and nitrous oxide, and general anaesthesia was maintained for up to 74 minutes. The action of medetomidine was reversed at the end of each procedure with atipamezole, and the animals recovered smoothly and uneventfully.

Use of rocuronium administered by continuous infusion in dogs

OBJECTIVE A clinical trial to determine whether continuous infusion administration technique was suitable for maintaining neuromuscular blockade with rocuronium bromide in dogs. ANIMALS Twenty-two dogs, 10 males and 12 females, median age 2 years 4 months, median weight 32 kg undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. MATERIALS AND METHODS After induction of anaesthesia, neuromuscular function was evaluated using train-of-four (TOF) stimulation of the dorsal buccal branch of the facial nerve. A bolus dose of 0.5 mg kg-1 rocuronium was administered intravenously and an infusion of 0.2 mg kg-1 hour-1 was started immediately. Neuromuscular blockade was assessed visually by counting the number of twitches observed during TOF stimulation repeated at 10-second intervals. RESULTS The bolus dose of rocuronium abolished the response to TOF stimulation in 21 of the 22 dogs. The median onset time of neuromuscular blockade (complete loss of all four twitches) was 82 seconds (range 38-184 seconds). Median infusion duration was 76 minutes (range 20.3-146 minutes). CONCLUSIONS AND CLINICAL RELEVANCE This protocol of rocuronium administration was considered to be effective in dogs. Constant infusion of rocuronium is easily applicable to clinical practice and further work is required on infusion titration.

The clinical use of the neuromuscular blocking agent rocuronium in dogs

OBJECTIVE The aim of this study was to characterize the onset and duration of action of the aminosteroid muscle relaxant rocuronium in dogs under clinical conditions. STUDY DESIGN Prospective single dose trial. ANIMALS Twenty-three dogs aged between 6 months and 12 years, weighing between 5.5 and 61.5 kg admitted to the University of Liverpool Small Animal Hospital between January and March 2000, and undergoing elective surgical procedures under general anaesthesia. MATERIALS AND METHODS Following induction of general anaesthesia, neuromuscular function was evaluated using train-of-four (TOF) stimulation. An initial dose of 0.4 mg kg-1 rocuronium was administered intravenously (IV) and neuromuscular blockade was monitored by visually assessing the number of responses (twitches) to TOF stimulation (train-of-four count: TOFC). Incremental doses of 0.16 mg kg-1 rocuronium were administered as indicated, when at least two twitches of the TOFC had returned. RESULTS Rocuronium (0.4 mg kg-1) abolished all responses to TOF stimulation in all dogs. The mean time to onset of neuromuscular blockade (complete abolition of all twitches) was 98 ± 52 seconds. Neuromuscular blockade (absence of all twitches to return of all four) lasted 32.3 ± 8.2 minutes. Incremental doses of 0.16 mg kg-1 had a mean duration of action of 20.8 ± 4.9 minutes and up to seven increments were shown to be noncumulative. The effects of rocuronium were readily antagonized with neostigmine and atropine. Small transient increases in arterial blood pressure, which occurred in three dogs after the administration of rocuronium, were the only cardiovascular side-effects observed. CONCLUSIONS Rocuronium is an effective nondepolarizing neuromuscular blocking agent in the dog, with a rapid onset of neuromuscular block after intravenous administration and an intermediate duration of action. CLINICAL RELEVANCE Rocuronium produced a neuromuscular block with similar characteristics to those obtained with vecuronium, thus apparently offering little advantage over vecuronium. However, its availability in aqueous solution and a longer shelf-life increases convenience.

The use of the nondepolarizing neuromuscular blocking drug cis-atracurium in dogs

Objective This clinical trial attempted to evaluate the potency, onset and duration of action of cis-atracurium in dogs. Animals Twenty dogs aged between 1 and 15 years and weighing between 15 and 85 kg admitted for a variety of elective, surgical procedures under general anaesthesia. Materials and methods Following induction of general anaesthesia, the effects of an intravenous loading dose of cis-atracurium (0.1 mg kg-1) were evaluated by counting visual responses to train of four (TOF) nerve stimulation. Incremental doses of 0.02 or 0.04 mg kg-1 cis-atracurium were administered when the first of four responses to TOF stimulation was present. Results An initial dose of 0.1 mg kg-1 eliminated all four TOF responses in 18 out of 20 dogs. The same dose, repeated 10 minutes later in two animals in which blockade was incomplete, abolished all responses. In dogs receiving 0.1 mg kg-1 cis-atracurium neuromuscular blockade lasted 27.2 ± 9.3 minutes. Up to six incremental doses were given in individual animals; incremental doses appeared to be noncumulative. No untoward side-effects were observed with the use of this drug. There was considerable variation between individuals in response to cis-atracurium. Conclusions Cis-atracurium is an effective neuromuscular blocking agent in the dog, although its potency varies. Clinical Relevance Further studies are required to determine whether observed differences in potency are related to age, breed or sex. Cis-atracurium may prove useful in dogs with impaired renal and or hepatic function.

Reversal of neuromuscular block in companion animals

OBJECTIVE To review the evidence regarding the reversal of neuromuscular block (NMB) in companion animals with emphasis on the development and use of newer agents. DATABASE USED Data sources include scientific reviews and original research publications in both human and veterinary literature using Pubmed and Scopus as search data bases. Unpublished and locally published data on reversal of NMB are presented. CONCLUSIONS Residual NMB has been shown to increase morbidity and mortality in humans and needs to be avoided. It can be detected only by adequate neuromuscular monitoring. The proper use of reversal agents avoids residual NMB and recurarization should not occur. Anticholinesterase inhibitors, such as edrophonium and neostigmine have been used to reverse NMB when the need for this has been established. Reversal is influenced by several factors and a number of undesirable side- effects of these drugs have been reported. Sugammadex, a γ-cyclodextrin, which was designed specifically to encapsulate rocuronium, is more rapid in its actions, has fewer side effects and can reverse profound NMB induced by aminosteroidal muscle relaxants.

Reversal of profound rocuronium or vecuronium-induced neuromuscular block with sugammadex in isoflurane-anaesthetised dogs.

This study evaluated the use of sugammadex for reversal of profound neuromuscular blockade induced with rocuronium or vecuronium in dogs. Anaesthesia was induced and maintained with isoflurane in oxygen in eight dogs on two occasions. Neuromuscular blockade was monitored using peroneal nerve stimulation and acceleromyography. Rocuronium 0.6 mg/kg or vecuronium 0.1mg/kg was administered intravenously (IV), followed 5 min later by sugammadex 8 mg/kg IV. Lag and onset time of rocuronium and vecuronium, lag time from sugammadex injection to recovery of first twitch response, recovery of T1/T0 to 25% and 75%, recovery index, and time to recovery of the train-of-four ratio (T4/T1) to 0.9 were recorded. Cardiovascular and respiratory parameters were also noted. Statistical analysis was performed using one-way ANOVA. Onset time for rocuronium (37 ± 18s; [mean ± SD]) was significantly shorter than for vecuronium (62 ± 15s) (P<0.04). No other significant differences were found between the two groups. After both rocuronium and vecuronium blockade, T4/T1 recovered to 0.9 in under 2 min after sugammadex (58.1 ± 67.8s and 98.1 ± 70.3s, respectively; P<0.32). Sugammadex can reverse profound neuromuscular blockade induced by vecuronium or rocuronium safely and rapidly in isoflurane-anaesthetised dogs.

Association of Veterinary Anaesthetists – the beginnings

Following on the first recorded administration of a general anaesthetic to a human in Boston in 1846, in the form of ether, the news and the adoption of the technique rapidly spread to the UK. Within a year the technique had been used in most species of domestic animals. It was not until the Animals Anaesthetics Act 1919 that legislation was passed in the UK regulating the use of anaesthesia in animals. This had been preceded in 1915 by the publication of the first textbook on the subject by Hobday. Progress in the subject throughout the first half of the 20th Century was relatively slow with the possible exceptions of the development of epidural anaesthesia by Brook in 1935 and the publication of the book by Wright in 1940. The seminal paper on the use of balanced anaesthesia in the dog and cat led to further developments in the subject by Hall and Weaver in 1954. The introduction of halothane by Raventos in 1956 provided a further stimulus to the development of the subject. By the mid-1960’s each of the UK Veterinary Schools had an academic post devoted to the subject. On January 6th 1964 a group of six people met at Langford, University of Bristol to discuss the possibility of forming an association and to discuss postgraduate education in the subject with a view to establishing a qualification. The meeting had been initiated by Leslie Hall and Barbara Weaver and in addition Professor JG Wright, Ronald Jones, Ben Mitchell and Derek Tavernor were present. It was resolved to explore the formation of an association of veterinary anaesthetists with a minimum membership of fifteen people and to explore the possibility of initiating a diploma in veterinary anaesthesia. Professor Wright was appointed as the first President and Barbara Weaver as the first secretary. The secretary would communicate with people who had expressed an interest in or contributed to the subject and invite them to an inaugural meeting. This was held on April 3rd 1964 at the Royal Veterinary College in London and nineteen people attended and there were four apologies. It was agreed unanimously to proceed with the formation of the Association of Veterinary Anaesthetists of Great Britain and Ireland and Professor Wright was elected President, Barbara Weaver secretary and Derek Tavernor treasurer. The committee was elected as was James Campbell, Leslie Hall and Noel Ormrod. Initially there would be ordinary members for which there would be strict criteria and those six people who attended the Bristol meeting would be founder members. Provision would be made for associate, corresponding and honorary members at a later date. The annual subscription was fixed at 2 guineas (£2–10 p). This would enable fully paid-up members to attend all meetings without charge. The constitution would be formulated by the committee with the assistance of the Association of Anaesthetists, GB & I. It was reported that on the initiative of Professor W.L. Weipers, president of the Royal College of Veterinary Surgeons (RCVS), a group was formed to advise on the possible formation of a diploma in veterinary anaesthesia. The meeting to approve the constitution of the AVA was held in Liverpool on 5th June 1964. This was the first meeting to receive commercial sponsorship in that the British Oxygen Company provided funds for the hire of the venue, a buffet and mounted an exhibition of equipment. The first scientific and general meeting was held in Cambridge on 24–25th October 1964 on the subject of respiration and anaesthesia. The objectives of the Association were formulated and were: • To promote the study and development of anaesthesia in animals and the recognition of anaesthesia as a specialised branch of veterinary medicine. • To represent veterinary anaesthetists and to protect their interests.